Safety device for a pyrotechnic impact fuse of a ballistic high explosive shell

ABSTRACT

In a fuse-less shell ( 10 ) with a so-called pyrotechnic impact fuse bore safety and safety in front of the bore are achieved by a spring-supported ball ( 43 ) in a central bore ( 72 ) in a valve body ( 65 ). The valve body ( 65 ) separates an explosive charge ( 60 ) at the shell side from an impact-sensitive firing charge ( 28 ). The firing charge ( 28 ) is disposed within a shell cap ( 24 ) and surrounds a projection ( 30 ), which acts as an anvil, of the valve body ( 65 ).

[0001] The invention concerns a safety device for a pyrotechnic impactfuse of a ballistic high explosive shell as set forth in the classifyingportion of claim 1.

[0002] A safety device of that kind for a pyrotechnic percussion orimpact fuse is known from DE 195 44 458.2-21. A pyrotechnic materialwhich is fired upon impact is disposed in the ogive of the shell. Theinternal space in the shell is connected to the space in which thepyrotechnic material is disposed, by way of a central firing passage.Lateral firing passages open into the firing passage. The central firingpassage is also intended to accommodate a ball. The function of thisarrangement is to afford bore safety, in other words, while the shell ispassing through the barrel, any firing of the pyrotechnic material issealed off by the ball in the firing passage so that the explosivecharge in the interior of the shell body cannot be fired.

[0003] The object of the invention is to enhance the operationalreliability of the ball safety device.

[0004] In accordance with the invention that is attained in accordancewith the characterising features of claim 1. Developments of theinvention are set forth in the appendant claims.

[0005] The greater degree of functional reliability of the ball safetydevice is afforded by the spring element which acts on the ball. Thespring element ensures that the ball is seated in the safe position in acondition of being displaced back in the direction of the base, in asimple manner. In that situation the ball seals off the central firingpassage at the periphery thereof. It has surprisingly been found thatany firing gases or vapours which possibly pass around the ball arestopped or rendered harmless by the spring element to such an extentthat the subsequently arranged boosting charge is not fired. Any firinggases or vapours experience multiple reduction due to the spring elementwhich is also in a condition of contact therearound and are in partdeflected in a centripetal direction where they are mutually reduced ornullified in respect of their energy.

[0006] An embodiment of the invention is illustrated in the drawing inwhich:

[0007]FIG. 1 is a view in longitudinal section of a shell,

[0008]FIG. 2 shows a view on an enlarged scale of a portion of the shellshown in FIG. 1, and

[0009]FIG. 3 shows the portion of FIG. 2 in a safety function.

[0010] A ballistic shell 1 of a 40 mm calibre comprises a shell body 10with an annular groove 11 for a propellent charge sleeve (not shown), aone-piece screwthreaded ring 12, a guide ring 6, a base screw 2, ahollow space or cavity 13 with an explosive charge 60, a valve body 65and a cap 24.

[0011] The valve body 65 and the cap 24 are screwed to the screwthreadedring 12 by way of screwthread connections 66 and 67.

[0012] Disposed in the hollow space 26 between the valve body 65 and theshell cap 24 is a firing charge 28 comprising an impact-sensitivesecondary explosive.

[0013] The valve body 65 bears with a collar 68 both against an end face69 of the screwthreaded ring 20 and also with a collar 70 against anannular face 71 of the shell cap 24. Those structural features preventso-called through-firing of explosive gases or vapours from thedetonated secondary explosive 28 to the explosive charge 60, suchthrough-firing effect occurring at the periphery of the arrangement.

[0014] In addition the collar 68 protects the armour-piercingscrewthreaded ring 12 from the explosive action of the firing charge 28.The step portion 15 of the shell body 10 also contributes to thearmour-piercing capability.

[0015] A transition 9 from the cylindrical inside wall 16 to the cone 17of the shell body 10 forms a desired-rupture location which is indicatedas a wavy line 8. Upon detonation of the explosive charge 60 the shellbody 10 tears at the desired-rupture location 8 and accelerates the stepportion 15 with the screwthreaded ring 12 in the form of a one-piecepart for the purposes of piercing armour.

[0016] A projection portion 30 of the valve body 65 has lateral firingpassages 41 and a two-stage central bore 72. The central bore 72 isdivided into a ball guide 42 with a ball 43, a plate member 44 which isheld in place by a crimp flange, a compression coil spring 73 and a bore77.

[0017] The ball 43 comprises brass and provides sealing integrity at theperiphery thereof in particular in a portion 74 of the central bore 72,insofar as the periphery of the ball 43 is supported with a closeclearance in the ball guide 42. The ball 43 can also comprise anothermaterial such as steel or plastic material.

[0018] The compression coil spring 73 is slightly prestressed between ashoulder 75 and the ball 43. It has a central passage 76 in the usualway. The diameter of the bore 77 of the central bore 72 approximatelycorresponds to the diameter of the central passage 76.

[0019] A conical charge 29 comprising a secondary explosive is arrangedin a conical recess 80 adjoining the bore 77. That conical charge 29serves as a boosting charge. The conical charge 29 bears with its largebase 31 over a large area against the explosive charge 60. In that waythe charge 29 has a high pulse action, in the sense of a pointed conicalhollow charge.

[0020] The hollow space 13 in the shell body 10 is provided at the ogiveside with a conical portion 14. The explosive charge 60 correspondinglybears with its conical portion 63 against the conical charge 29. Theconical portion 63 has a free end face 62 which is in contact with thebase 31 of the charge 29 in such a way as almost to cover the areathereof, that is to say almost 100%.

[0021] During the acceleration phase of the shell 1 in a canon (notshown) the ball 43 is carried on the compressed compression coil spring73 as shown in FIG. 3, by virtue of the mass inertia of the ball 43.

[0022] While the shell 1 is passing through the barrel and during thesubsequent part of its trajectory of between 2 and 3 meters, thearrangement guarantees that firing of the firing charge 28 due to anyrandom event does not result in firing of the conical charge 29 and thusfiring of the explosive charge 60. The ball 43 seals off the centralbore 72 in the portion 74 at the periphery in respect of pressure andfiring gases and vapours. That affords bore safety and also safety infront of the bore for between about 2 and 3 meters in front of thebarrel.

[0023] If the firing charge 28 should be fired either while the shell ispassing through the bore or outside the bore, that is to say in theregion of safety in front of the bore, the shell 1, after termination ofthe ballistic trajectory, is a dud which can be readily cleared.

[0024] Dangerous firing means are not to be found either in the firedfiring charge 28 or in the unfired firing charge 28.

[0025] After the phase involving safety in front of the bore, that is tosay after the ball 43 has been moved by the compression coil spring 73out of the sealing position in FIG. 3 into the armed position shown inFIG. 2, the firing charge 28 is fired upon impact of the shell 1 againstthe target. The firing charge 28 is pressed shock-like against theprojection portion 30 of the valve body 65, which acts as an anvil, andfired as a result. Firing vapours and gases pass under high pressurethrough the lateral firing passages 41 into the free central bore 72 andfire the conical charge 29. That then fires the explosive charge 60. Inthat way the shell 1 detonates, with fragmentation of the shell body 10.

[0026] In the case of a lightly armoured target the firing charge 28admittedly detonates. At the same time the armour is pierced. Thescrewthreaded ring 12 with the step portion 15 produces the penetrationeffect so that detonation of the shell 1 occurs in the interior of thetarget.

1. A safety device for a pyrotechnic impact fuse of a ballistic high explosive shell, comprising a pyrotechnic mass which fires upon impact, wherein a ball safety device only passes into the armed position after launch of the shell, and wherein a central firing passage (72) is arranged in a penetration passage of a valve body (65) and is provided with a ball guide (42) with spaced end abutments (44, 75) for a ball (43) mounted therein, and lateral firing passages (41) open into the central firing passage (72) behind the ball (43) in the armed position, characterised in that a prestressed spring element (73) is disposed between the ball (43) and the abutment (75) on the explosives side, and the ball (43) in the safe position seals off the firing passage (72) with the lateral firing passages (41) opening into the firing passage (72), against firing vapours flowing therethrough.
 2. A safety device according to claim 1 characterised in that the ball (43) is in peripheral sealing relationship with the wall of the ball guide (42).
 3. A safety device according to claim 1 characterised in that the ball (43) comprises metal such as steel, brass or plastic material.
 4. A safety device according to claim 1 characterised in that the spring element is in the form of a coil spring (73) with a central passage (76).
 5. A safety device according to claim 1 characterised in that the penetration core (18) is screwed to the shell body (10).
 6. A safety device according to claim 1 characterised in that the valve body (65) has at the exit side in a conically enlarging opening (80) an explosive charge (29) which bears over a large area against a main explosive charge (60) of the high explosive shell (1). 